1. Field of the Invention
The present invention relates to a housing structure of an electronic keyboard musical instrument, which includes a housing adapted to be completed by fixing an upper case to a lower case.
2. Description of the Related Art
A conventional housing structure of an electronic keyboard musical instrument generally includes upper and lower cases formed separately from each other and fixedly fastened together by fastening means. However, with the housing structure having upper and lower cases completely separated from each other before being fastened together, these must be placed in different places during assembly for production and maintenance for services, resulting in a low efficiency of working space.
There is also known a housing structure including upper and lower cases separately formed and coupled for pivotal motion relative to each other. For example, a housing disclosed in Japanese Laid-open Utility Model Registration No. 62-103382 includes an upper case pivotable between open and closed states relative to a lower case around a hinge provided at the rear of the housing. This housing is completed by fixing the upper case to the lower case by screws or the like, with the upper case kept retained in a closed state.
However, according to the above-described housing disclosed in Japanese Laid-open Utility Model Registration No. 62-103382 in which the upper and lower cases are coupled by a hinge, it is not easy to release the coupling therebetween to separate them from each other.
Thus, it is difficult to, for example, mount component parts to the housing after the upper case has been fixed to the lower case. In some cases, the sequence of operations is therefore restricted such that component parts must be mounted to the housing before the upper and lower cases being coupled together.
Since the upper and lower cases being coupled together by a hinge are difficult to uncouple, it is inconvenient for an operator to see the interior of the housing for maintenance purpose, for example, resulting in low workability.
On the other hand, in the case of using, instead of a hinge, a pivotal coupling device for pivotably coupling upper and lower cases together, safety cannot be assured if the pivotal coupling is unintentionally decoupled when the upper case is open. Furthermore, if the pivotal coupling is unintentionally decoupled when the upper case is closed, the upper and lower cases are misaligned in position, which makes it difficult for an operator to again fasten them together.
Conventionally, there has also been known a housing structure of an electronic keyboard musical instrument, in which upper and lower cases are formed separately from each other and a housing is completed by fixedly mounting the upper case to the lower case (Japanese Patent Publication No. 3821022). In a housing structure of this type, the upper and lower cases are generally fastened together by fastening means such as screws applied from above or from below.
To fix the upper and lower cases together, these must be fixed after being arranged in a proper positional relation. In some electronic keyboard musical instrument, arms and side beds are fixed beforehand to the upper case, and key slips and a keyboard unit are fixed beforehand to the lower case. In such a musical instrument, if a positional accuracy between the upper and lower cases is low, gaps between the keyboard unit and the side beds become nonuniform between left and right sides of the instrument or vary depending on position in the forward-to-backward direction of the instrument. On the other hand, in a musical instrument having a keyboard unit fixed beforehand to the upper case, if the positional accuracy between the upper and lower cases is low, gaps between key slips and the keyboard unit and between the key slip and side beds become inappropriate. Thus, it is necessary to fix the upper and lower cases together while adjusting the gaps.
When the upper and lower cases are fixed by screws or the like inserted from below, there is a problem of requiring cumbersome operations. Specifically, the upper and lower cases are first turned upside down for being fixed together and then turned right side up to visually check whether the gaps are uniform between the left and right sides of the musical instrument. If the gaps are not uniform, the upper and lower cases are turned upside down to perform the fixing operation again.
When the upper and lower cases are fixed by screws inserted from above, it is unnecessary to turn the upper and lower cases upside down. However, the screws or other fastening means become visible from above even after completion of assembly of the housing, posing a problem of inferior external appearance.